Engineering Commons^™

Surface Modification To Improve The Electrochemical Performance Of Cathode Materials For Lithium-Ion Batteries And Sodium-Ion Batteries, Han Yu

Doctoral Dissertations

"The specific capacity of active materials as well as their cycling stability are the main limiting factors for the performance of lithium-ion batteries (LIBs) and sodium-ion batteries (SIB). Atomic layer deposition (ALD) is considered as a promising surface modification method to enhance the electrochemical performance of active materials for LIBs and SIBs.

In this research, we are committed to using ALD to modify the cathode materials of LIB, by coating different films on the surface of different cathode materials and constructing a stable and favorable interface layer for lithium-ion transport, so that we can protect the active materials from the …

Oxidation Of Silicon Carbide And Graphite For High Temperature Gas-Cooled Reactor Applications, Adam Thomas Bratten

Doctoral Dissertations

"This research focuses on the oxidation behavior of silicon carbide and matrix grade graphite, specifically as it pertains to accident scenarios in Gen IV thermal spectrum high temperature gas cooled nuclear reactors. It is imperative to understand the oxidation behavior of such materials to predict their response to off-normal environments and certify their accident tolerance to implement Gen IV reactors. The onset of oxidation temperature of matrix graphite was found to have a strong dependence on the microstructure, and therefore processing parameters, of the materials. The A3-3 type grade contained regions of partially graphitized carbon that were more disordered and …

Processing And Characterization Of Tini-Based Alloys Fabricated By Laser Aided Manufacturing, Yitao Chen

Doctoral Dissertations

"Laser powder-based directed energy deposition (DED) is a major laser aided additive manufacturing (AM) process for metals. It applies laser energy to deposit metal powders to form 3D metal parts. Apart from manufacturing traditional alloys, DED can also be used to develop advanced alloys with the novel idea of elemental powder mixture feedstock. TiNi-based alloy is a type of shape memory alloy (SMA), a smart material with unique shape memory effects. Using laser powder DED to synthesize TiNi-based SMAs from elemental powder mixture can create more possibilities in new compositions and properties. It can also overcome the limitations of conventional …

Use Of Cellular Concrete For Air Convection Embankment To Protect Permafrost Foundation In Cold Regions, Hanli Wu

Doctoral Dissertations

"Crushed-rock air convection embankment (ACE) has been used to mitigate thaw settlement, and pavement distresses caused by climatic extremes in permafrost regions for over three decades. However, the desired crushed rocks needed for ACE are not readily available in many areas of interior Alaska. Burdened by the need to ship suitable rocks to remote locations, the cost of constructing an ACE is often prohibitively high, which prevents its wide use in Alaska. An existing cementitious material, cellular concrete, may provide the solution.

This study intends to systematically characterize the heat transfer patterns of ACE and identify the performance benefits of …

Computational Fluid Dynamics Techniques For Multiphase Flow Systems, Jose Sebastian Uribe Lopez

Doctoral Dissertations

"Mathematical modelling of multiphase flow systems has been a major and persistent challenge over the last decades. Vast attempts to obtain predictive models can be found reported in literature, where major advances can be recognized in recent years, paired to enhancements in computer science and engineering. Notwithstanding, universally valid models with a mechanistic development are far from being achieved. The current status of modelling any multiphase flow system relies on the model order reduction of purely theoretical models. Such reductions and simplifications become the source of deviations in the predictions of the experimentally measured parameters and will constrain the applicability …

Theoretical Determination Of The Yield Curve For Unsaturated Soils, Sara Fayek

Doctoral Dissertations

"An important step to developing a good understanding of the behavior of unsaturated soils is to adopt a formal and simple constitutive framework and to conduct high-quality and short-time experiments. Barcelona Basic Model (BBM) was the first elastoplastic constitutive model for unsaturated soils. The yield curve, which separates the elastic region from the elastoplastic region, is an important aspect of constitutive modeling for unsaturated soils. Most concepts for unsaturated soils were developed based upon the results from suction-controlled triaxial (SCTX) tests. Though, the SCTX tests on unsaturated soils are costly, time-consuming, and laborious, and their results are questionable. This study …

Pi And Emi Analysis Of 3d Ic System With Tsvs And Co-Packaged Optics, Wei Zhang

Doctoral Dissertations

"With the demand for developing high-capacity, high-density, high-power optical links for data center communications, co-packaged optics is a promising solution. When the three-dimensional (3D) IC and optic engines are integrated into the same package, the design of such systems in terms of signal integrity, power integrity, and electromagnetic interference will be more challenging.

This first paper mainly focuses on modeling the bias-voltage-dependent, temperature-dependent, and light-intensity-dependent hysteresis behavior of a through-silicon-vias (TSV) structure in 3D IC and analyzing its effect on the power integrity of a system with 3D IC.

This second paper investigates the scaled tendency of the emissions in …

Synergistic Effect Of Shrinkage Mitigating Strategies On Performance Of Fiber-Reinforced Cementitious Composites, Kamran Aghaee

Doctoral Dissertations

"The advantages of using shrinkage mitigating strategies to reduce shrinkage and mitigate cracking of concrete is well documented. However, the benefits and drawbacks of employing multiple strategies have not been explored. The main objective of this study is to provide insights into the mechanisms of using multiple strategies to enhance shrinkage and cracking resistance to promote the properties of high-performance cementitious composites (HPC) designated for infrastructural construction, repair, and 3D printing applications. HPC mixtures were prepared with steel and synthetic macro and microfibers, expansive agent (EA), and shrinkage reducing admixture (SRA) coupled with various curing methods e.g., internal curing using …

The Effect Of Mass Transport On Deposit Quality In Copper Electrowinning, Joseph Bauer

Doctoral Dissertations

"Roughness and nodulation of copper electrodeposits depend strongly on mass transfer conditions of copper ions to the electrode surface. Mass transfer properties in electrowinning electrolytes were first characterized. The effective diffusivity of cupric ion was measured with a rotating disk electrode in CuSO₄-H₂SO₄ electrolytes at temperatures relevant to electrowinning, with and without additives. Adding 20 mg L^-1 of chloride ion increased the measured diffusion coefficient, but commercial smoothing additives had little effect. An empirical formula to predict cupric diffusivity was generated for later use in mass transport modeling.

Boundary layer thickness information for commercial …

Strain And Temperature Measurement From Distributed Fiber Optic Sensors In Performance-Based Fire Engineering, Yanping Zhu

Doctoral Dissertations

"Strain and temperature measurement of steel and concrete structures under fires is critical to the understanding of structural performance yet historically challenging due to a significant gap in measurement science. This Ph.D. study characterizes in six parts low-cost distributed fiber optic sensors and applies them to strain, and temperature measurements based on Rayleigh and Brillouin light scattering. The first part aims to quantify the Rayleigh scattering based measurement accuracy of distributed fiber optic sensors under a heating-holding load protocol and characterize the effect of polymer coating on the sensors as the polymer softens and melts at elevated temperatures. The second …

Accuracy Improvement Of Cable Harness Modeling & Analytical Modeling Of Multi-Reflections In High-Speed Signal Channels, Muqi Ouyang

Doctoral Dissertations

"Cable harnesses are widely used in modern vehicles to power electric systems locating at different locations throughout the vehicle and to establish signal channels for data communications between these systems. Generally, a cable harness consists of multiple wires and its geometry can be very complicated, making full-wave modeling and simulation approaches computational resource-intensive. To cut down the computational effort, the hybrid multiconductor transmission-line (MTL) method has been developed, and the generalized MTL (GMTL) method and the multiple scattering (MS) method have been developed to improve the accuracy of the hybrid MTL method. In this research, the convergence issue in the …

Groundwater Withdrawal Estimation Using Integrated Remote Sensing Products And Machine Learning, Sayantan Majumdar

Doctoral Dissertations

"The rising demands for water, food, and energy primarily driven by the increasing global population constitute a pressing issue worldwide. Therefore, the water-food-energy nexus plays a substantial role in developing globally applicable sustainable solutions. Recent technological advancements, including the earth observation programs using spaceborne remote sensing platforms, have enabled us to monitor various critical components affecting the globe. Groundwater, which comprises the world's 30% freshwater, is one such key component of the global water resources and supplies nearly half of the global drinking water.

Despite groundwater overdraft in many parts of the world, including the United States (US), there are …

Promoting Distributed Energy Deployment And Diffusion For Sustainable Civil Infrastructure Using Multi-Agent Based Modeling And Quantitative Analytics, Gasser Ali

Doctoral Dissertations

"Distributed Solar Generation (DSG) using small-scale Photo-Voltaic (PV) is an evolving technology with increasingly growing market penetration due to its significant benefits to consumers and broader power systems. DSG is sustainable, provides reliability, and is cost-effective where solar energy is abundant. However, the increasingly growing adoption of DSG creates uncertainties in forecasting electric power demand and market behavior. It also causes concerns of a “utility death spiral”. To this end, the goal of this research is to critically analyze the diffusion and benefits of DSG in the electric power infrastructure as a complex System-of-Systems (SoS). Specifically, this dissertation addresses the …

Multifunctional Behaviors Of Two-Dimensional Materials And Their Composites, Yanxiao Li

Doctoral Dissertations

"Two-dimensional (2D) materials, including graphene, transition metal carbides or nitrides (TMC/Ns), have rich surface chemistry, superb electrical and mechanical properties. These unique properties make them ideal for multifunctional devices. Among them, we focused on graphene and TMC/Ns (i.e., MXenes), as well as their composites. Unlike the well-known graphene, MXenes, are relatively new and typically synthesized by the selective etching of the “A” layers from the layered carbides and /or nitrides known as MAX phases, which introduce MXenes with rich terminal groups (e.g. -O-, -OH, -F).

During my Ph.D. study, firstly, the adhesive and frictional behaviors, which are related to successful …

Molten Steel Interactions With Tundish Linings And Refractory Glazes, Tyler Michael Richards

Doctoral Dissertations

"In the final stages of casting, molten steel is in contact with two main types of refractories: the working lining of the tundish used to serve as an intermediate vessel between the ladle and copper mold, and the various glazed carbon-bearing refractories used to control the flow of steel from the ladle to the tundish and from the tundish to the mold. If steel interacts with these refractories in such a way as to result in the formation of inclusions, it may be too late to remove them, leading to degradation of the steel’s mechanical properties. Understanding these interactions and …

Influences Of The Internal Residual On Combustion Instabilities In The Misfire And Partial Burn Regimes Of A Dilute Spark-Ignition Engine, Rachel Inez Stiffler

Doctoral Dissertations

"Dilution in spark-ignition (SI) engines can improve fuel consumption and reduce emissions; however, increased levels of dilution either from excess oxidizer or exhaust gas recirculation (EGR) causes combustion to become more strained and cycle-to-cycle variations increase. At high levels of dilution incomplete combustion events (i.e. misfires and partial burns) start to occur, which cause combustion instabilities and eventually a dilute limit is reached. It is known the combustion instabilities seen are primarily due to the feed-forward mechanism present in the residual gases, but it is still unknown what about the residual is influencing the dynamics under high levels of dilution …

Optimization Of Energy Storage Scheduling In Electricity Markets, Jian Liu

Doctoral Dissertations

"In the existing literature, merchants' trading actions are usually assumed not to affect market prices; however, a large-scale energy storage merchant’s actions can affect market prices. This work examined two electricity merchant scenarios: one with only energy storage and the other with both energy storage and renewable power plants. We approximated market impact via a linear function of the electricity traded by the merchant. This study began by applying dynamic programming to the optimal economic dispatch policy of electricity merchants and it considered the market impact, physical characteristics of storage systems, and the uncertainty of renewable energy sources. Then, this …

Resistivity Imaging Of Prominent Seepage Pathways In Karst Terrain, Abdullah Hadi Zaid Alhaj

Doctoral Dissertations

"An integrated research approach was conducted to evaluate subsurface karstic conditions in Greene County, southwestern Missouri. Electrical resistivity tomography (ERT) was employed to image anomalously low resistivity zones associated with the presence of seepage pathways that were anthropogenic and/or natural in origin. Techniques including visual inspection (VI), multichannel analysis of surface waves (MASW), borehole control (BC), and aerial imagery (AI) were supplementally used to constrain the ERT data interpretations.

This research addressed six objectives. First, the ERT data interpretations were verified in terms of depth to the top of bedrock, fractures/voids, and moisture changes using the MASW, borehole control, and …

Novel Ferromagnetic Materials With Improved Mechanical Performance, Wesley Alexander Everhart

Doctoral Dissertations

"The ductility of intermetallics has long been a hindrance to their broad adaptation despite a significant range of properties such as magnetic, half-metallic, and shape memory behavior. The lack of a general theory for the ductility of intermetallics along with the lack of prior art that experimentally measured mechanical properties drives the need for significant investment in many of these novel magnetic materials in order to even understand, let alone correct, poor ductility.

This dissertation includes work that explored the effect of vanadium content and quenching rate on the microstructure and ductility of Fe-Co alloys. Results indicated that a martensitic …

Sensitivity Of The Two-Fluid Model To Constitutive Correlations For Large Diameter Pipes, Alexander Lee Swearingen

Doctoral Dissertations

"Multiphase flows are a significant factor in nuclear reactor operations. In order to understand this behavior in reactor systems, system analysis codes are used to simulate reactor conditions. Due to the nature of the nuclear industry, simulations predicting the void development in the core are required to be highly accurate. This work evaluated the sensitivity of the void fraction and interfacial area concentration predictions to changes in correlations used to calculate three parameters that are used to complete the interfacial drag calculation. The three parameters evaluated were drift-flux, void fraction covariance, and interfacial area concentration. The change in drift-flux correlation …

Investigating The Interaction Between The Recycled Components And The Asphalt Binders, Plant, Lab, And Field Mixes, Eslam Deef-Allah

Doctoral Dissertations

"Modifying asphalt binders and mixes with recycled components is common practice due to their environmental and economic merits. Literature has indicated that different recycled components interact with (blend with) asphalt differently, ranging from no blending, partial blending, or full blending. The degree of blending between recycled components and virgin asphalt binders (VABs) and the exchanged components impact the performance of modified asphalt binders. However, the nature of the interaction process between the recycled components and the VABs is not fully understood. The primary objective of this study was to explore the interactions between recycled components and VABs. By understanding the …

Using Computational Methods To Optimize High Heat Flux Component Thermal Performance In Magnetic Confinement Fusion Reactor Research, Monica Gehrig

Doctoral Dissertations

"Heat transfer enhancement by means of internally modified geometries in tubes and channels is an important mechanism to improve the survivability of components in extreme high-heat flux environments. Various features such as ribs and fins are studied using computational fluid dynamics in both uniform and one-sided heating in tubes and rectangular channels respectively to determine the most effective geometries across a variety of different flow and heating conditions. This work examines heat transfer enhancement and rib geometry optimization to support experimental research for nuclear fusion applications. The project begins by designing and analyzing test sections supporting a helium flow loop …

Far-End Crosstalk Modeling And Prediction For High-Speed Pcb Design With Inhomogeneous Dielectric Layers (Idls), Yuanzhuo Liu

Doctoral Dissertations

"Far-end crosstalk (FEXT) noise is a critical factor that affects signal integrity performance in high-speed systems. The FEXT level is sensitive to the inhomogeneity of the dielectric layers in fabricated printed circuit boards (PCB). The stripline is laminated by multiple inhomogeneous dielectric layers (IDL). The dielectric layers of the stripline are laminated with epoxy resin and glass bundles. The dielectric permittivity of the epoxy resin and glass bundles are different, which causes the inhomogeneity of the dielectric layers while also increasing the FEXT magnitude. The dielectric of the microstrip in printed circuit boards (PCB) fabrication usually consists of two layers: …

Deep Learning-Based Surrogate Models For Post-Earthquake Damage Assessment, Xinzhe Yuan

Doctoral Dissertations

"Seismic damage assessment is a critical step to enhance community resilience in the wake of an earthquake. This study aims to develop deep learning-based surrogate models for widely used fragility curves to achieve more accurate and rapid assessment in practice. These surrogate models are based on artificial neural networks trained from the labelled ground motions whose resulting damage classes on targeted structures are determined by nonlinear time history analyses. The development of various surrogate models is progressed in four phases. In Phase I, the multilayer perceptron (MLP) is used to develop multivariate seismic classifiers with up to 50 hand-crafted intensity …

Catalytic Carbon Dioxide Hydrogenation To Methanol/Dimethyl Ether Over Copper-Based Catalysts, Xiao Fan

Doctoral Dissertations

Direct synthesis of dimethyl ether (DME) via CO₂ hydrogenation has received great attention, owing to the global warming caused by CO₂ emission and increasing energy demand worldwide. In this works, three major aspects of bifunctional catalysts development were studied: (1) investigation of the roles of interaction in the CuO-ZnO-ZrO₂-Al₂O₃/HZSM-5 bifunctional catalysts, (2) deactivation and regeneration of CuO-ZnO-ZrO₂-Al₂O₃ with different zeolitic catalysts for one-step CO₂ hydrogenation to dimethyl ether, and (3) study on the enhancement of activity and stability of CZZA/HZSM-5 bifunctional catalysts via the introduction of …

Assessment Of Rib Failure Mechanisms Using Discontinuum Mechanics Based Modeling Approach, Maurice Nuonituo Sunkpal

Doctoral Dissertations

"Coal mine rib failures are major safety and health challenge for coal mines worldwide. The need for clear procedures to evaluate mine rib behavior and to provide an efficient, reliable, and consistent rib control protocol is needed. Understanding coal rib geomechanics is essential for improving rib stability and eliminating fatality and injury trends due to rib failures. This knowledge is also vital to determine support requirements.

The rib control practices used in the 21st Century in most countries originated in roof control techniques. Understandably, applying roof control methods to coal rib does not yield desirable results. The geology of structures …

Development Of In-Situ Radiometric Inspection Methods For Quality Assurance In Laser Powder Bed Fusion, Cody S. Lough

Doctoral Dissertations

“Laser Powder Bed Fusion (LPBF) metal Additive Manufacturing (AM) fabricates 3D metal parts layer-by-layer. The process enables production of geometrically complex parts that are difficult to inspect with traditional methods. The LPBF parts experience significant geometry driven thermal variations during manufacturing. This creates microstructure and mechanical property inhomogeneities and can stochastically cause defects. Mission critical applications require part qualification by measuring the defects non-destructively. The layer-to-layer nature of LPBF permits non-intrusive measurement of radiometric signals for a part’s entire volume. These measurements provide thermal features that correlate with the local part health. This research establishes Optical Emission Spectroscopy (OES) and …

Studying The Effects Of New Additive Materials For The Improvement Of The Capacity And Cycle Life Performance Of The Lead-Acid Battery, Julian Kosacki

Doctoral Dissertations

"Lead-acid batteries are an established technology with nearly 99% recyclability; however, lead-acid batteries produce only 40% of their theoretical capacity due to poor active mass utilization and PbSO4 pore blockage, and the longevity of the batteries is hampered by secondary reactions during the cycle life such as corrosion and gassing.

Lead-acid batteries were investigated and improved through several different approaches: an alternative electrolyte to mitigate secondary reactions, graphite additives to improve positive active mass (PAM) utilization, and dispersant additives to help the industrial pasting process.

The thermodynamics and chemical reactions of a commercial electrolyte replacement called Tydrolyte^TM were investigated …

Investigating The Impact Of Rock Bridges On The Mechanical Behavior Of Jointed Rock Mass Using Lattice Spring-Based Synthetic Rock Mass (Ls-Srm) Approach, Mariam Salem Alebayat

Doctoral Dissertations

"Rock bridges were defined as a segment of intact rock that separates from discontinuities. Numerous studies are focused on developing methods to quantify their significance in rock mass strength and deformability behavior. This thesis aimed to enhance understanding of the effect of rock bridges on jointed rock masses in both laboratory and slope scales. For this purpose, the lattice spring base Synthetic Rock Mass (LS-SRM) method was adopted to conduct the numerical models, distinguished in computational efficiency, and simulates the brittle failure and roughness of discontinuities.

A robust approach was developed to optimize the calibration procedure to avoid the complex …

Thermomechanical Simulation And Process Optimization For Hot Rolling Of Steel, Shouvik Ganguly

Doctoral Dissertations

"Hot rolling is a manufacturing process that involves large material deformation, complicated geometries, contact conditions and non-uniform temperature gradients. Steel industries are motivated to prevent hot rolled steel products to be defect free and with desired shape and size. In order to simulate the process accurately, it is essential that the material model for steel accounts for the viscoplasticity and changes in properties that occur in steel at elevated temperatures as grain growth and recrystallization.

The healing of existing voids during hot rolling was investigated using finite element simulations. Voids are highly undesirable as they not only degrade the product …